1. Field of the Invention
The present invention relates generally to a device for controlling the temperature of a conductive member, and to a gas chromatography system incorporating such a device.
2. Description of the Related Art
Temperature control is widely performed in many fields, such as gas chromatography. In gas sample chromatography, a system typically includes a section for cooling and collecting gas. The section collects rarefied sample gas in a trap tube by concentrating the sample gas, conveys the gas into a column at a relatively narrow zone, and separates the sample gas into its components. Such a gas chromatography system is widely used in the field of analysis or measurement of gas. It is desirable to collect sample gas in the trap tube and convey the trapped sample gas into the column accurately and rapidly. In order to accomplish this, accurate and rapid sensing and control of the temperature at the trap tube is required.
The trapping system for gas chromatograph conventionally measures the temperature of the trap tube only locally, however, because it senses the temperature with a sensor, such as a metal thermistor or a metal theromcouple close to the trap tube or with a direct joint of the trap tube. As a result, it is difficult to sense and control the temperature correctly.
Rapid temperature sensing is often difficult because of the comparatively large heat capacity of the temperature sensor itself and its fixture, and thus there is a delay in the thermal sensing. Such a delay is significant if the thermistor is jointed to the tube directly because the heat capacity at the joint of the thermistor and the tube becomes large. As a result, it is difficult to sense and control the temperature rapidly.
According to one aspect of the present invention, there is provided a device for controlling the temperature of a conductive member, comprising:
means for detecting the electric resistance of the conductive member;
means for calculating the temperature of the conductive member based on the electric resistance detected by means for detecting the electric resistance; and
means for adjusting the temperature of the conductive member based on the temperature calculated by means for calculating the temperature.
With the above-mentioned element according to the invention, the temperature of the conductive member such as a trap tube used for gas chromatograph is calculated using the detected electric resistance of the conductive member instead of detecting the temperature by the thermistor or the thermocouple. As a result, the mean temperature of the conductive member can be calculated, and thus it is possible to control the temperature of the conductive member correctly. Also, it is possible to control the temperature of the conductive member rapidly, because there is no delay resulting from the heat capacity of the conductive member.
The device according to the present invention can be applied to many fields including the gas chromatographic system.
Preferably, means for detecting the electric resistance comprises:
means for applying the pulse electric current with a predetermined pulse width to the conductive member at a predetermined time interval; and
means for detecting the voltage generated by applying the pulse electric current.
As the pulse current with the predetermined pulse is applied to the conductive member at the predetermined interval, unnecessary heating is avoided. Thus, as a heavy-current can be applied to the conductive member, it is possible to detect extremely small electric resistance at the order of 10xe2x88x924 xcexa9. Also, when the current is applied to the conductive member at the predetermined, e. g. a relatively short time interval, the voltage of the conductive member can be always detected while the pulse current is applied. Therefore, it is possible to control the temperature of the conductive member following the rapid temperature change. As a result, more accurate temperature control can be performed.
In this case, the electric resistance of the conductive member is determined by the detected voltage.
More preferably, means for adjusting the temperature comprises:
means for cooling the conductive member by spraying a coolant; and
means for heating the conductive member by applying the pulse electric current to the conductive member.
By such cooling and/or heating, it is possible to cool and/or heat the conductive member rapidly, and thus it is possible to control the temperature of the conductive member rapidly.
According to another aspect of the present invention, there is provided a gas chromatography system comprises a chromatograph, a trap tube for collecting gas to be supplied to the chromatograph, the trap tube consisting of a conductive material, and a device for controlling the temperature of the trap tube, comprising:
means for detecting the electric resistance of the conductive member such as the trap tube;
means for calculating the temperature of the conductive member based on the electric resistance detected by means for detecting the electric resistance; and
means for adjusting the temperature of the conductive member based on the temperature calculated by means for calculating the temperature.
With the above-mentioned element according to the invention, it is possible to control the trap tube accurately and rapidly, and thus a separation of trapped sample gas into components consisting of the sample gas can be performed at high accuracy.
According to one preferred embodiment, the trap tube is made from stainless steel.
In view of the foregoing, it is an object of the present invention to provide a device for controlling the temperature of the conductive member, e. g. a trap tube consisting of a conductive material correctly and rapidly.
It is another object of the present invention to provide a trapping system for a gas chromatograph comprising such a device.